Vitamin D Dose Requirements for Fracture Prevention

To the Editor: In a recent pooled analysis of vitamin D dose requirements for fracture prevention, Bischoff-Ferrari and colleagues (July 5 issue) 1 reanalyzed data from clinical trials by taking into account vitamin D supplementation taken by participants in addition to the study medication. This reanalysis provides a more accurate estimation of the vitamin D intake. However, the results are inconclusive because the authors did not mention sunlight exposure, which is the natural physiological source of vitamin D. This substance is not a “vitalamine” but it is a secosteroid hormone that is normally produced by the skin. No dietary intake is . . .